This invention relates to a process and apparatus for electrolytically refining spent fuel from a nuclear reactor and recovering purified uranium and a mixture of uranium and plutonium for use as fresh blanket and core fuels in a nuclear reactor. More particularly, this invention relates to a process and apparatus for refining spent blanket and core fuel in a single electrorefining cell by dissolving uranium and plutonium from the spent fuel in a molten cadmium pool, electrolytically depositing purified uranium on one cathode and subsequently electrolytically depositing a mixture of uranium and plutonium on a second cathode.
Electrorefining processes have been generally used to recover high purity metal or metals from impure feed materials and more particularly, to recover metals, such as uranium and plutonium, from spent nuclear fuel. Electrorefining of spent nuclear fuel is carried out in an electrolysis cell of the kind disclosed in U.S. Pat. Nos. 2,951,793 and 4,596,647. In such cells, the spent nuclear fuel forms the anode, or is dissolved in a anode pool. An electrolyte of fused salts is used, and the purified metal is transferred electrolytically and collected on the cathode. In other designs, the anode pool is located at the bottom of the cell, and the cathode may be located above the anode in an electrolyte pool.
While the electrorefining process and apparatus currently used to recover uranium and plutonium from spent nuclear fuel have certain advantages, it is by necessity a multi-stage operation to obtain both uranium and a mixture of uranium and plutonium for use as blanket and core fuels in nuclear reactors. This multi-stage operation includes the steps of electrorefining the spent blanket fuel in an electrolysis cell to obtain uranium and plutonium, separating the uranium and plutonium obtained from the blanket fuel by halide slagging, adding the recovered plutonium to the electrolyte pool in the electrolysis cell to enrich the core fuel and then electrorefining the spent core fuel to obtain a mixture of uranium and plutonium. In addition, this process uses solid cathodes in electrolysis cells which provide for the recovery of uranium and plutonium sequentially, rather than simultaneously. This process features results in an increased concentration of plutonium in the electrolyte salt which is undesirable. Accordingly, a new electrorefining process and apparatus are derived which eliminate the multistage operation and provide for the sequential recovery of uranium and a mixture of uranium and plutonium to be used as new blanket and core fuel, respectively.